HIGH-TEMPERATURE IN-SITU FTIR SPECTROSCOPY STUDY OF LAOF AND BAF2 LAOF CATALYSTS FOR METHANE OXIDATIVE COUPLING/

In situ FTIR spectroscopy was used to characterize the oxygen adspecie s and its reactivity with CH4 over LaOF and 15 mol% BaF2/LaOF catalyst s at OCM temperature (750-800 degrees C). It was found that gas-phase oxygen was activated on the surface of LaOF and 15 mol% BaF2/LaOF, whi ch had been pretreated under vacuum at 750 or 800 degrees C, forming O -2(-) species at high temperature (750-800 degrees C). At 750 degrees C, the adsorbed O-2(-) species can react with pure CH4 accompanied by formation of gas-phase C2H4 and CO2, and there is a good correlation b etween the rate of disappearance of surface O-2(-) and the rate of for mation of gas-phase C2H4. The O-2(-) species was also observed over th e catalysts under working condition, and it reacted with CH4 in a mann er that was consistent with its role in a catalytic cycle. These resul ts suggest that O-2(-) may be the active oxygen species for OCM reacti on over these catalysts.